Frand terms allow smartphone manufacturers to use standard technology, such as the signalling systems that connect mobile devices to networks. They guarantee that the company that holds a patent cannot discriminate against others that want to use the same technology, and cannot charge excessive licensing fees.

The investigation into whether “Samsung has failed to honour its irrevocable commitment” to Frand terms, given in 1998, was prompted by a barrage patent infringement cases from the firm. It is suing Apple over at least 13 patents related to 3G.

“The opening of proceedings means that the Commission will examine the case as a matter of priority,” the European Commission said.

The investigation marks a major regulatory intervention in Samsung’s bitter patent dispute with Apple, which is ongoing in courts in the United States, Germany and Australia, among other jurisdictions. The European Commission sent the two firms requests for information in November.

Apple alleges that Samsung’s Galaxy range of smartphones and tablets are “slavish” copies of the iPhone and iPad designs, and has sought injuntions to ban them from sale. The Korean firm, now the world’s biggest manufacturer of smartphones, has retaliated by claiming Apple has infringed its 3G technology.

According to Florian Mueller, a German technology consultant who has chronicled the mobile industry’s patent wars on his blog, the European Commission’s action could cause firms suing over patent infringement of standard technology to think twice.

“Even though Samsung is at this stage the only company to be investigated over this issue, other suspected abusers could face similar inquiries anytime,” he said.

“And everyone else who may intend to seek or enforce injunctions based on Frand-pledged-standards-essential patents in Europe will now have to proceed with extra caution.”

Mr Mueller said the intellectual property rights Apple has sued Smasung over are meanwhile not covered by Frand terms.

"In principle, anti-trust agencies could also try to go after Apple, but in that case, the theory would have to be a different one than Frand-pledged standards-essential patents," he said.